Motorcycle thefts are on the decline, and of five major brands, only Harley-Davidson owners saw an uptick in the number of stolen bikes in 2013, new data from the National Insurance Crime Bureau show.

It’s hard to say why more Harleys continue to be stolen, but some speculate the riders are too trusting – leaving their bikes unlocked and unattended because most fellow riders won’t mess with them.

Still, there were 3,907 Harley-Davidsons stolen in the U.S. last year, up 4 percent from 2012, while the percentage of stolen Honda, Yamaha, Kawasaki and Suzuki motorcycles fell 2.1 percent (Kawasaki) to 9.1 percent (Suzuki), according to data from the trade association based in Des Plaines, Ill.

Overall, there were 45,367 motorcycle thefts reported in the U.S. in 2013, down 1.5 percent, even as bike sales increased.

The thefts were highest in California, followed by Florida, Texas, North Carolina and Indiana.

Nationwide, Honda was the bike stolen most often, followed by Yamaha, Suzuki, Kawasaki and Harley-Davidson.

At least one motorcycle theft ring has in the past targeted motels along the routes of biker rallies, stealing bikes from parking lots.

The bike, which Bidwell valued at $45,000, was stolen on a Sunday afternoon in May.

The bar was packed with people, Bidwell said, and he had just showed the bike to some of them three minutes earlier.

“We parked right in front of the bar. I was 15 feet from it,” he said, about where the motorcycle was parked.

No one reported seeing the theft take place, Bidwell said. The bike was unlocked and could be started without a key.

Bidwell has since published a plea on Facebook seeking information about the theft.

“We are not going to give up until she is home,” the plea says.

Thousands of people have viewed the posting, and some of them swore they saw the bike in various places.

“Someone said they thought they saw it near Nashville (Tenn.),” Bidwell said about the motorcycle, which had $29,340 in accessories and had won nine custom motorcycle competitions.

“My word to everybody is ‘lock up your bike.’ I cannot stress that enough,” he said.

There have been similar brazen thefts of motorcycles in Wisconsin’s Fox Valley this spring, including one bike stolen from the parking lot of a movie theater.

Generally, there aren’t many motorcycle thefts at biker rallies.

“People are very trusting. It’s a Harley brotherhood, and under no circumstances do you touch somebody else’s bike without their permission,” Bidwell said.

There’s an unwritten honor code among motorcycle enthusiasts, but unfortunately it’s not enough to deter thieves, said Menasha (Wis.) Police Officer Aaron Zemlock, who recently investigated the theft of a Harley-Davidson from the parking lot of Graphic Packaging Corp. in the middle of the day.

The bike was in plain view of the street and the packaging plant. The thief, still not caught, was seen on a surveillance camera driving away and nearly causing an accident in the intersection.

“It looked like he was dropped off by another vehicle, walked up to the bike, and was there for less than two minutes,” Zemlock said.

“It was bold, absolutely,” he added.

Thirty seven percent of the motorcycles reported stolen in the U.S. in 2013 were recovered, compared with about 50 percent of the stolen cars, according to the National Insurance Crime Bureau.

“In some cases, fairly rare bikes have been recovered, including a 1953 Triumph that was returned to its rightful owner 53 years later. He is 73 years old now,” said Roger Morris, spokesman for the insurance crime bureau.

Often, bikes are cut up and sold for parts. The parts, or intact motorcycles, are sometimes shipped overseas where they’re worth much more and can’t be easily traced.

“We have found barrels of motorcycle parts being shipped out of the country,” Morris said.

Locks, alarms, and parking your motorcycle in a secure location are still the best theft deterrents, although a bike can be stolen in seconds, according to the National Insurance Crime Bureau.

“Have good insurance. You would be surprised at how many people don’t have theft coverage,” Morris said.